1. Field of the Invention
The present invention relates to a X-ray apparatus, more particularly, it relates to a digital X-ray apparatus mainly used in the field of medical equipment.
2. Description of the Related Art
An X-ray apparatus is widely used in various fields, particularly in the medical field. Conventionally, as an X-ray apparatus having high sensitivity and high resolution, there is a digital X-ray apparatus displaying an image on a cathode-ray tube (CRT) instead of a conventional X-ray film.
The digital X-ray image can be obtained by the following steps. That is, when the X-ray is irradiated on to an object, for example, a human body, the X-ray transmitted through the object is exposed on a stimulable phosphor plate constituted by a sheet-like fluorescence medium which is able to accumulate a part of the X-ray energy. When the photostimulable phosphor plate is scanned by an excitation beam (for example, a laser beam), the accumulated energy is excited by the laser beam and a fluorescent light is emitted from the photostimulable phosphor plate.
The fluorescent light is collected by collection equipment, for example, bundled optical fibers, and converted to analog electrical signals by an optical-to-electrical converter. Further, the analog electrical signals are converted to digital signals to obtain the digital X-ray image on the CRT.
Conventionally, however, some problems occur in this method when obtaining the X-ray image. That is, there is deterioration in the characteristics (for example, S/N ratio) of the photostimulable phosphor plate caused by absorption of moisture, and further by damage or dust on the photostimulable phosphor plate and optical device including the laser beam adjuster. This deterioration, causes an abnormal picture on the X-ray image displayed on the CRT which may result in an incorrect diagnosis when an operator evaluates the displayed image.
Accordingly, the most important matter of the digital X-ray apparatus is to increase the precision of the X-ray image so as to prevent incorrect diagnosis caused by abnormal picture elements on the displayed image. Therefore, it is necessary to detect abnormal picture elements before the X-ray apparatus is actually used for diagnosis. Further, it is necessary to display a distribution state of the abnormal picture elements, and to generate an alarm message when the number of the abnormal picture elements exceeds a predetermined threshold level.